Disulfide process

Abstract

Disulfides are produced in high yields and high purity by a process comprising first converting thiols to alkali metal mercaptides by treatment with an alkali metal hydroxide in a reaction medium comprising N-methylpyrrolidone, N-methylpyrrolidone/water, and isopropanol/water and then reacting the mercaptide with elemental sulfur in the reaction medium to form the disulfide.

I claim: 
     
       1. An improved process for the production of disulfides which comprises the steps of: I. reacting (a) at least one mercaptan with (b) at least one alkali metal hydroxide in (c) a reaction medium comprising N-methylpyrrolidone, N-methylpyrrolidone/water, and isopropanol/water under conditions which produce an alkali metal mercaptide and   Ii. adding sufficient sulfur to the reaction mass of step (I) containing said alkali metal mercaptide to oxidize the mercaptide to the disulfide and heating the reaction mass containing the added sulfur to a temperature and for a period of time sufficient to cause the reaction product to contain a substantial preponderance of disulfide.   
     
     
       2. A process according to claim 1 wherein the mercaptan is an aliphatic or cycloaliphatic mercaptan having the general formula RSH in which R is an alkyl or cycloalkyl radical having from 1 to 20 carbon atoms. 
     
     
       3. A process according to claim 1 wherein the reaction medium is N-methylpyrrolidone and the amount of reaction medium present is sufficient to keep the weight percent solids below about 35 percent. 
     
     
       4. A process according to claim 1 wherein said reaction medium is a 50/50 weight percent mixture of N-methylpyrrolidone and water and the amount of reaction medium present is sufficient to keep the weight percent solids below about 35 percent. 
     
     
       5. A process according to claim 1 wherein the reaction medium is about a 50/50 weight percent mixture of isopropanol and water and the amount of solvent present is sufficient to keep the weight percent solids below about 35 percent. 
     
     
       6. A process according to claim 1 wherein the temperature of reaction is about 65° to about 350° F (18.3°-177° C) and the time of reaction is in the range of about 1 to about 3 hours and the pressure is in the range of about 0 to about 150 psig. 
     
     
       7. A process according to claim 1 wherein the mercaptan is tertiary-butyl mercaptan and the disulfide is di-tert-butyl disulfide and the alkali metal hydroxide is sodium hydroxide. 
     
     
       8. A process according to claim 1 wherein said reacting is carried out at the reflux temperature.